What's a Coffee Defect?
As an agricultural product, coffee seeds are subject to a certain percentage of defects. Some defects will negatively impact the flavor and aroma, while others are just ugly. The SCA guidelines for green coffee defects separate them into two categories: Category One for primary defects, and Category Two for secondary imperfections. To earn the distinction of a Specialty Coffee grade, a sample may contain zero primary and a maximum of five secondary defects.
Even the best coffees sometimes contain a few small defects. Broken or chipped beans are common. Occasionally, a few immature or underripe seeds are present, even in high-scoring samples. Almost every roaster in the world will tell you they've encountered a small stone, rock, or piece of metal in an otherwise pristine bag of coffee.
Identifying and removing these intruders is just part of the job. On smaller roasters, operators will scan coffee in the cooling tray and pick out any outliers, like underdeveloped "quakers" that don't take on the same color as the rest of the batch. On larger production roasters, destoners and optical sorters filter out foreign objects or irregular seeds.
Sorting green coffee using a green grading mat
Frequency of Defects at Specialty Roasteries
At Mill City Roasters' production facility, we only use specialty-grade coffees for our wholesale and toll roasting programs. Defects are rare on our cupping table when we're evaluating our own product. But as consultants, we regularly taste coffees from other companies to provide guidance or feedback, and we encounter defects more frequently during that work.
While highly defective coffee is rare, we've certainly seen our fair share. Clients have brought us a green that they purchased at a "too good to be true" price, only to find out that it was riddled with serious issues, like mold and bug damage.
Our Most Commonly Tasted Defect
By far, the most common defect we taste at Mill City Roasters is aged greens. Whether we're evaluating green coffee for a client or providing a roasted coffee evaluation, old green coffee is a frequent cause of decreased flavor quality. Old greens taste like a wet newspaper or paper grocery bag. Coffee people will sometimes use the term "baggy" to describe the flavor. The defect is perceptible in light, medium, and sometimes even darker roasts. Some greens take over a year to start to taste stale; others will begin to lose quality after only 6 months post-arrival.
The reason roasters are using old greens is simple. It's a financial choice. They either over-purchased coffee when it was fresh and ended up with more than they could use before it lost its life. Or, they purchased past-crop coffee because it was discounted.
A Home for Old Greens
No matter the reason, many roasters will end up with old greens at some point. We never recommend throwing out green coffee. There should always be a home for it in your lineup, either in a super dark blend that roasts well past second crack, or in something like a flavored coffee. Hopefully, you can move through that coffee quickly and adjust your ordering to avoid the overage in the future.
